The Food and Drug Administration approved avapritinib for adult patients with advanced systemic mastocytosis, including patients with aggressive systemic mastocytosis (ASM), systemic mastocytosis with an associated haematological neoplasm (SM-AHN), and mast cell leukaemia (MCL).

Efficacy was evaluated in EXPLORER (NCT02561988) and PATHFINDER (NCT03580655), two multi-centre, single-arm, open-label clinical trials enrolling patients with AdvSM.

The main efficacy outcome measure was overall response rate (ORR) per modified IWG-MRT-ECNM criteria, as adjudicated by a central committee. Additional efficacy measures were duration of response (DOR), time to response, and changes in individual measures of mast cell burden. Fifty-three patients received daily doses of avapritinib, up to 200 mg.

The ORR in all evaluable patients in both trials combined was 57% (95% CI: 42, 70) (n=53), with 28% complete remissions and 28% partial remissions. The median duration of response was 38.3 months (95% confidence interval: 19, not estimable) and the median time to response was 2.1 months.

The most common adverse reactions (incidence ≥ 20%) in patients with AdvSM were oedema, diarrhoea, nausea, and fatigue/asthenia.

Avapritinib is not recommended for the treatment of patients with AdvSM with platelet counts of less than 50 X 109/L.

The recommended avapritinib dose is 200 mg orally once daily for patients with AdvSM.

View full prescribing information for avapritinib here.

Source: FDA